Gravitational potential energy

• Gravitational Potential Energy

  • Energy in the gravitational potential store of an object is defined as: The energy an object has due to its height in a gravitational field
  • This means:
  • If an object is lifted up, energy will be transferred to its gravitational store 
  • If an object falls, energy will be transferred away from its gravitational store 
• • The gravitational potential energy of an object can be calculated using the equation:

  E = m g h

  • Where:
  • E = change in gravitational potential energy, in joules (J)
  • m = mass, in kilograms (kg)
  • g = gravitational field strength in newtons per kilogram (N/kg)
  • h = change in height in metres (m)
• Elastic Potential Energy

  • Energy in the elastic potential store of an object is defined as: The energy stored in an elastic object when work is done on the object
  • This means that any object that can change shape by stretching, bending or compressing (eg. springs, rubber bands)
  • When a spring is stretched (or compressed), work is done on the spring which results in energy being transferred to the elastic potential store of the spring
  • When the spring is released, energy is transferred away from its elastic potential store
• • The amount of elastic potential energy stored in a stretched spring can be calculated using the equation:
  • Where:
  • Ee = elastic potential energy in joules (J)
  • k = spring constant in newtons per metre (N/m)
  • x = extension in metres (m)
  • The above equation assumes that the spring has not been stretched beyond its limit of proportionality

  
• Energy Transfers in a Vertical Spring

  • When a vertical spring is extended and contracted, energy is transferred
  • Although the total energy of the spring system will remain constant, energy will be transferred between
  • The elastic potential energy store
  • The kinetic energy store
  • The gravitational potential energy store